The AP courses work as a kind of supplement in the US high school education system. The AP courses cater excellent US high school students to study the college level courses in advance when they are content with the basic high school courses and want to push further to a higher level. But the AP is nothing but an examination of knowledge with the only goal to help good students to save time, money by transferring credits when entering college. While the IB curriculum forms a self-complete education and evaluation system putting its goal in fostering the ten great merits possessed by IB students. It is ability cultivation oriented through the carrier of knowledge. Only in terms of knowledge difficulty can we claim that the higher level IB courses are on par with the AP courses.